I had to work my way up to liking spicy foods. I'm still nowhere near Howie's tolerance level, but I'm working on it. When I married him, Taco Bell's nacho cheese sauce was very spicy to me...Now I can handle some crushed red pepper seed or the flesh of jalepeno peppers (just not the ribs and seeds from them, not just yet, anyway). Like him, though, I don't like heat just for sake of heat; it has to be flavorful as well as add a little kick.
This article about peppers, What Makes Peppers Hot, Hot, Hot!
is both entertaining and informative. Enjoy!